Father undergoes brain surgery after 'one-punch attack'

A father-of-three is fighting for life and has undergone brain surgery after he was one-punched while trying to help a friend during a brawl outside a Frankston pub.

Family of the Doveton man Beau Shortis said he was leaving an engagement party Frankston's The Grand Hotel with friends shortly after midnight, when two men allegedly approached the group shouting obscenities.

A fight broke out between the groups and Mr Shortis, a 34-year-old factory worker, was allegedly punched from behind.

The force of the blow caused him to fall to the ground, cracking his skull on the concrete path.

The 34-year-old factory worker was punched in the head. (Supplied)

Mr Shortis’ sister, Donna Griffiths, told 9NEWS her brother is a “not a fighter” and is a hard working family man who would never incite violence.

“He's a very placid person,” Ms Griffiths said.

“He's definitely not a fighter. He's always the peacekeeper.

“He's got three little beautiful children waiting for him. He needs to survive. He needs to.”

Beau Shortis underwent brain surgery today. (Supplied)

Tragically for the family, Mr Shortis’ uncle died in hospital from illness this morning while his 7-year-old nephew died last week.

"We have been through hell and back, they say bad things come in threes and we are just hoping Beau pulls through this, but it's not looking positive," Ms Griffiths said.